Chemistry · Sample Paper 2

General instructions

Section A · Objective

1. Question 11 mark

   The molality of a solution containing 2 mol of solute in 500 g of water is

   1. A.1 m
   2. B.2 m
   3. C.4 m
   4. D.0.25 m
2. Question 21 mark

   Which aqueous solution has the highest boiling point?

   1. A.0.1 M glucose
   2. B.0.1 M NaCl
   3. C.0.1 M CaCl₂
   4. D.0.1 M urea
3. Question 31 mark

   The SI unit of molar conductivity is

   1. A.S m${}^{-1}$
   2. B.S m${}^2$ mol${}^{-1}$
   3. C.Ω m
   4. D.S cm${}^{-1}$
4. Question 41 mark

   In the electrolysis of aqueous NaCl, the product at the cathode is

   1. A.Na
   2. B.Cl₂
   3. C.H₂
   4. D.O₂
5. Question 51 mark

   For a zero-order reaction, the rate

   1. A.depends on concentration
   2. B.is independent of concentration
   3. C.doubles when concentration doubles
   4. D.is zero
6. Question 61 mark

   A catalyst increases the rate of a reaction by

   1. A.increasing activation energy
   2. B.lowering activation energy
   3. C.increasing ΔH
   4. D.shifting equilibrium
7. Question 71 mark

   The lanthanoid contraction is due to

   1. A.poor shielding by 4f electrons
   2. B.poor shielding by 5d electrons
   3. C.increase in nuclear size
   4. D.decrease in mass
8. Question 81 mark

   Which of these is a bidentate ligand?

   1. A.NH₃
   2. B.Cl⁻
   3. C.ethane-1,2-diamine
   4. D.H₂O
9. Question 91 mark

   Chloroform on exposure to light and air forms

   1. A.CCl₄
   2. B.phosgene
   3. C.CH₂Cl₂
   4. D.chlorine
10. Question 101 mark

    Which is the most acidic?

    1. A.ethanol
    2. B.phenol
    3. C.p-nitrophenol
    4. D.p-cresol
11. Question 111 mark

    The reagent used to distinguish aldehydes from ketones is

    1. A.Tollens' reagent
    2. B.NaOH
    3. C.HCl
    4. D.Br₂ water
12. Question 121 mark

    The Hofmann bromamide reaction converts an amide into an amine with

    1. A.one more carbon
    2. B.one less carbon
    3. C.the same number of carbons
    4. D.two less carbons
13. Question 131 mark

    Assertion (A): A solution of acetone in chloroform shows negative deviation from Raoult's law.

    Reason (R): Hydrogen bonds form between acetone and chloroform molecules.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
14. Question 141 mark

    Assertion (A): [Fe(CN)₆]³⁻ is an inner orbital complex.

    Reason (R): CN⁻ is a strong-field ligand that causes pairing of 3d electrons, giving d²sp³ hybridisation.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
15. Question 151 mark

    Assertion (A): Ethers are less soluble in water than alcohols of similar molecular mass.

    Reason (R): Ethers cannot form hydrogen bonds with water.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
16. Question 161 mark

    Assertion (A): Glucose does not give a test with Schiff's reagent.

    Reason (R): Glucose exists mainly in a cyclic hemiacetal form with very little free aldehyde.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.

Section B · Very short answer

1. Question 172 marks

   Calculate the mole fraction of ethanol in a solution containing 46 g of ethanol and 90 g of water.

2. Question 182 marks

   How much charge is required to deposit 5.4 g of silver from AgNO₃ solution? (Ag = 108)

3. Question 192 marks

   What is the effect of temperature on the rate of reaction? Write the Arrhenius equation and explain its terms.

4. Question 202 marks

   Why do transition elements form complexes? Give two reasons.

5. OR

   Question 202 marks

   Write the balanced equation for the oxidation of Fe²⁺ by acidified K₂Cr₂O₇.

6. Question 212 marks

   Arrange in increasing order of basic strength in aqueous solution: CH₃NH₂, (CH₃)₂NH, (CH₃)₃N, NH₃. Give reason.

Section C · Short answer

1. Question 223 marks

   200 cm³ of an aqueous solution of a protein contains 1.26 g of protein. The osmotic pressure at 300 K is $2.57\times 10^{-3}$ bar. Calculate the molar mass of the protein. ($R=0.083$ L bar mol⁻¹ K⁻¹)

2. Question 233 marks

   The conductivity of 0.001 M acetic acid is $4.95\times 10^{-5}{\text{S cm}}^{-1}$. Calculate its degree of dissociation if ${\Lambda }_m^{\circ }=390.5{\text{S cm}}^2{\text{mol}}^{-1}$.

3. Question 243 marks

   What is a pseudo-first-order reaction? Give one example. Why is it called so?

4. Question 253 marks

   Write the IUPAC name, hybridisation and magnetic behaviour of $[Co{F}_6{]}^{3-}$.

5. OR

   Question 253 marks

   Explain with examples: (i) linkage isomerism (ii) ionisation isomerism (iii) geometrical isomerism.

6. Question 263 marks

   Complete the reactions: (i) CH₃CH₂Br + KOH (alc) → (ii) C₆H₅Cl + Na + CH₃Cl (dry ether) → (iii) CH₃Br + AgCN →

7. Question 273 marks

   How will you convert: (i) propene to propan-2-ol (ii) phenol to salicylaldehyde (iii) ethanol to ethoxyethane?

8. Question 283 marks

   Give reasons: (i) Carboxylic acids do not give reactions of the carbonyl group. (ii) Chloroacetic acid is stronger than acetic acid. (iii) Aldehydes are more reactive than ketones towards nucleophilic addition.

Section D · Case-based

1. Question 294 marks

   Case study — Radioactive dating. Carbon-14 decays by first-order kinetics with a half-life of 5730 years. Living organisms keep a constant ratio of ¹⁴C to ¹²C; after death, the ¹⁴C content decreases. An archaeologist finds a wooden tool whose ¹⁴C activity is 25% of that in living wood.

   (i) Why does radioactive decay follow first-order kinetics? (1 mark)

   (ii) Calculate the rate constant for the decay of ¹⁴C. (1 mark)

   (iii) Find the age of the wooden tool. (2 marks)

   OR

   (iii) What fraction of ¹⁴C will remain after 17 190 years? Show your reasoning. (2 marks)

2. Question 304 marks

   Case study — Dyes from diazonium salts. When aniline is treated with sodium nitrite and dilute HCl at 273–278 K, benzenediazonium chloride is formed. It reacts with phenol in alkaline medium to give an orange dye, p-hydroxyazobenzene. Such azo dyes are widely used for colouring fabrics.

   (i) Why is the diazotisation reaction carried out at low temperature? (1 mark)

   (ii) Name the reaction in which a diazonium salt reacts with phenol. (1 mark)

   (iii) Write the equations for the formation of benzenediazonium chloride and its reaction with phenol. (2 marks)

   OR

   (iii) How is benzenediazonium chloride converted into (a) chlorobenzene (b) phenol? (2 marks)

Section E · Long answer

1. Question 315 marks

   (a) Define limiting molar conductivity and state Kohlrausch's law. (b) Calculate ${\Lambda }_m^{\circ }$ for CH₃COOH from: ${\Lambda }_m^{\circ }(HCl)=426$, ${\Lambda }_m^{\circ }(NaCl)=126$, ${\Lambda }_m^{\circ }(C{H}_{3}COONa)=91{\text{S cm}}^2{\text{mol}}^{-1}$. (c) Why does the molar conductivity of a strong electrolyte increase only slightly on dilution?

2. OR

   Question 315 marks

   (a) What is the van 't Hoff factor? How is it related to abnormal molar mass? (b) 2 g of benzoic acid (C₆H₅COOH) dissolved in 25 g of benzene shows a freezing point depression of 1.62 K. $K_f$ of benzene is 4.9 K kg mol⁻¹. Find the percentage association of the acid if it forms dimers.

3. Question 325 marks

   An organic compound A (C₃H₆O) does not reduce Tollens' reagent but gives a yellow precipitate with I₂/NaOH. On reduction it gives B, which on dehydration gives propene. Identify A and B and write the reactions. Also write the aldol condensation of ethanal.

4. OR

   Question 325 marks

   Write the reactions and conditions for: (i) Rosenmund reduction (ii) Clemmensen reduction (iii) Hell–Volhard–Zelinsky reaction (iv) Cannizzaro reaction (v) Etard reaction.

5. Question 335 marks

   (a) What are nucleic acids? Give two differences between DNA and RNA. (b) What is denaturation of proteins? (c) Name the vitamins whose deficiency causes (i) rickets (ii) night blindness.